Truncated HP1 lacking a functional chromodomain induces heterochromatinization upon in vivo targeting

Histochem Cell Biol. 2006 Jan;125(1-2):53-61. doi: 10.1007/s00418-005-0088-7. Epub 2005 Nov 10.

Abstract

Packaging of the eukaryotic genome into higher order chromatin structures is tightly related to gene expression. Pericentromeric heterochromatin is typified by accumulations of heterochromatin protein 1 (HP1), methylation of histone H3 at lysine 9 (MeH3K9) and global histone deacetylation. HP1 interacts with chromatin by binding to MeH3K9 through the chromodomain (CD). HP1 dimerizes with itself and binds a variety of proteins through its chromoshadow domain. We have analyzed at the single cell level whether HP1 lacking its functional CD is able to induce heterochromatinization in vivo. We used a lac-operator array-based system in mammalian cells to target EGFP-lac repressor tagged truncated HP1alpha and HP1beta to a lac operator containing gene-amplified chromosome region in living cells. After targeting truncated HP1alpha or HP1beta we observe enhanced tri-MeH3K9 and recruitment of endogenous HP1alpha and HP1beta to the chromosome region. We show that CD-less HP1alpha can induce chromatin condensation, whereas the effect of truncated HP1beta is less pronounced. Our results demonstrate that after lac repressor-mediated targeting, HP1alpha and HP1beta without a functional CD are able to induce heterochromatinization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CHO Cells
  • Chromatin / genetics
  • Chromatin / metabolism*
  • Chromatin / ultrastructure*
  • Chromosomal Proteins, Non-Histone / chemistry*
  • Chromosomal Proteins, Non-Histone / genetics
  • Chromosomal Proteins, Non-Histone / pharmacology*
  • Cricetinae
  • Fluorescent Antibody Technique
  • Heterochromatin / genetics
  • Heterochromatin / metabolism*
  • Histones / metabolism
  • Humans
  • Image Interpretation, Computer-Assisted
  • Lysine / metabolism
  • Methylation
  • Microscopy, Confocal
  • Plasmids / genetics

Substances

  • Chromatin
  • Chromosomal Proteins, Non-Histone
  • Heterochromatin
  • Histones
  • heterochromatin-specific nonhistone chromosomal protein HP-1
  • Lysine